[PATCH v6 1/2] tools/console: Add escape argument to configure escape character

[Peter Hoyes <peter.hoyes@xxxxxxx>]

From: Peter Hoyes <Peter.Hoyes@xxxxxxx>

Dom0 may be accessed via telnet, meaning the default escape character
(which is the same as telnet's) cannot be directly used to exit the
console. It would be helpful to make the escape character customizable
in such use cases.

Add --escape argument to console tool for this purpose.

Add argument to getopt options, parse and validate the escape character
and pass value to console_loop.

If --escape is not specified, it falls back to the existing behavior
using DEFAULT_ESCAPE_SEQUENCE.

Signed-off-by: Peter Hoyes <Peter.Hoyes@xxxxxxx>
Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
Reviewed-by: Hongda Deng <hongda.deng@xxxxxxx>
---
Changes in v5:
- Add this changelog

Changes in v4:
- Improve validation of the escape_character optarg

Changes in v3:
- Re-add the Reviewed-By tag accidentally removed in v2

Changes in v2:
- Drop the tags intended only for internal use at Arm

 tools/console/client/main.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/tools/console/client/main.c b/tools/console/client/main.c
index 6775006488..d2dcc3ddca 100644
--- a/tools/console/client/main.c
+++ b/tools/console/client/main.c
@@ -42,7 +42,7 @@
 #include <xenstore.h>
 #include "xenctrl.h"
 
-#define ESCAPE_CHARACTER 0x1d
+#define DEFAULT_ESCAPE_CHARACTER 0x1d
 
 static volatile sig_atomic_t received_signal = 0;
 static char lockfile[sizeof (XEN_LOCK_DIR "/xenconsole.") + 8] = { 0 };
@@ -77,6 +77,7 @@ static void usage(const char *program) {
               "  -n, --num N      use console number N\n"
               "  --type TYPE      console type. must be 'pv', 'serial' or 
'vuart'\n"
               "  --start-notify-fd N file descriptor used to notify parent\n"
+              "  --escape E       escape sequence to exit console\n"
               , program);
 }
 
@@ -174,7 +175,7 @@ static void restore_term(int fd, struct termios *old)
 }
 
 static int console_loop(int fd, struct xs_handle *xs, char *pty_path,
-                       bool interactive)
+                       bool interactive, char escape_character)
 {
        int ret, xs_fd = xs_fileno(xs), max_fd = -1;
 
@@ -215,7 +216,7 @@ static int console_loop(int fd, struct xs_handle *xs, char 
*pty_path,
                        char msg[60];
 
                        len = read(STDIN_FILENO, msg, sizeof(msg));
-                       if (len == 1 && msg[0] == ESCAPE_CHARACTER) {
+                       if (len == 1 && msg[0] == escape_character) {
                                return 0;
                        } 
 
@@ -335,6 +336,7 @@ int main(int argc, char **argv)
                { "help",    0, 0, 'h' },
                { "start-notify-fd", 1, 0, 's' },
                { "interactive", 0, 0, 'i' },
+               { "escape",  1, 0, 'e' },
                { 0 },
 
        };
@@ -345,6 +347,7 @@ int main(int argc, char **argv)
        console_type type = CONSOLE_INVAL;
        bool interactive = 0;
        const char *console_names = "serial, pv, vuart";
+       char escape_character = DEFAULT_ESCAPE_CHARACTER;
 
        while((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
                switch(ch) {
@@ -375,6 +378,16 @@ int main(int argc, char **argv)
                case 'i':
                        interactive = 1;
                        break;
+               case 'e':
+                       if (optarg[0] == '^' && optarg[1] && optarg[2] == '\0')
+                               escape_character = optarg[1] & 0x1f;
+                       else if (optarg[0] && optarg[1] == '\0')
+                               escape_character = optarg[0];
+                       else {
+                               fprintf(stderr, "Invalid escape argument\n");
+                               exit(EINVAL);
+                       }
+                       break;
                default:
                        fprintf(stderr, "Invalid argument\n");
                        fprintf(stderr, "Try `%s --help' for more 
information.\n", 
@@ -493,7 +506,7 @@ int main(int argc, char **argv)
                close(start_notify_fd);
        }
 
-       console_loop(spty, xs, path, interactive);
+       console_loop(spty, xs, path, interactive, escape_character);
 
        free(path);
        free(dom_path);
-- 
2.34.1